1) To set a background color: Change the Environment in the "Environment Texture" to an RGB Color node, and set the color to white. Pls see the manual for details -
http://render.otoy.com/manuals/AutoCAD/?page_id=466.
2) Wooden Grain material going in the wrong direction: Yes - this is because AutoCAD does not provide accurate UV coordinates to plugins. You simply need to rotate the material 90 degrees (via the Image Transform). I note you have setup Box projection on the screenshoot you have provided which will also work, but UV projection may be better in this case. Once you have converted an AutoCAD material to an Octane material and adjusted it "Save As Default", so the next time you use that AutoCAD material, the saved Octane material will be used - which will save you a lot of time. See the manual for details.
http://render.otoy.com/manuals/AutoCAD/?page_id=35
3) AutoCAD glass material: I thought that most AutoCAD transparent materials would automatically convert to Octane Specular materials - however there may be some that don't. If you can give me the AutoCAD glass material name which is not correctly converted I will investigate.
4) Sky Lighting. With HDR lighting - the lighting comes from a HDR image - so you cannot change the background color (since the background color is coming from the image). If instead you select "Daylight" lighting, you can adjust the sunset and sky colors. Only perspective camera mode is supported by the plugin at this stage.
5) AutoCAD metal material conversion: AutoCAD does not provide an indication to a plugin that a material is "metal", so you will need to make some small modifications to the converted Octane material. Generally this will involve increasing the "index". You can also download many metal materials from the Octane LiveDb which provide incredibly realistic metal renders. Once you have an AutoCAD metal material the way you want it, "Save as Default" so that that Octane setup is next used when you use that AutoCAD material.
Hope that addresses your concerns.
Paul